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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.animation;
     18 
     19 import android.view.animation.AnimationUtils;
     20 
     21 /**
     22  * This class provides a simple callback mechanism to listeners that is synchronized with all
     23  * other animators in the system. There is no duration, interpolation, or object value-setting
     24  * with this Animator. Instead, it is simply started, after which it proceeds to send out events
     25  * on every animation frame to its TimeListener (if set), with information about this animator,
     26  * the total elapsed time, and the elapsed time since the previous animation frame.
     27  */
     28 public class TimeAnimator extends ValueAnimator {
     29 
     30     private TimeListener mListener;
     31     private long mPreviousTime = -1;
     32 
     33     @Override
     34     public void start() {
     35         mPreviousTime = -1;
     36         super.start();
     37     }
     38 
     39     @Override
     40     boolean animateBasedOnTime(long currentTime) {
     41         if (mListener != null) {
     42             long totalTime = currentTime - mStartTime;
     43             long deltaTime = (mPreviousTime < 0) ? 0 : (currentTime - mPreviousTime);
     44             mPreviousTime = currentTime;
     45             mListener.onTimeUpdate(this, totalTime, deltaTime);
     46         }
     47         return false;
     48     }
     49 
     50     @Override
     51     public void setCurrentPlayTime(long playTime) {
     52         long currentTime = AnimationUtils.currentAnimationTimeMillis();
     53         mStartTime = Math.max(mStartTime, currentTime - playTime);
     54         mStartTimeCommitted = true; // do not allow start time to be compensated for jank
     55         animateBasedOnTime(currentTime);
     56     }
     57 
     58     /**
     59      * Sets a listener that is sent update events throughout the life of
     60      * an animation.
     61      *
     62      * @param listener the listener to be set.
     63      */
     64     public void setTimeListener(TimeListener listener) {
     65         mListener = listener;
     66     }
     67 
     68     @Override
     69     void animateValue(float fraction) {
     70         // Noop
     71     }
     72 
     73     @Override
     74     void initAnimation() {
     75         // noop
     76     }
     77 
     78     /**
     79      * Implementors of this interface can set themselves as update listeners
     80      * to a <code>TimeAnimator</code> instance to receive callbacks on every animation
     81      * frame to receive the total time since the animator started and the delta time
     82      * since the last frame. The first time the listener is called,
     83      * deltaTime will be zero. The same is true for totalTime, unless the animator was
     84      * set to a specific {@link ValueAnimator#setCurrentPlayTime(long) currentPlayTime}
     85      * prior to starting.
     86      */
     87     public static interface TimeListener {
     88         /**
     89          * <p>Notifies listeners of the occurrence of another frame of the animation,
     90          * along with information about the elapsed time.</p>
     91          *
     92          * @param animation The animator sending out the notification.
     93          * @param totalTime The total time elapsed since the animator started, in milliseconds.
     94          * @param deltaTime The time elapsed since the previous frame, in milliseconds.
     95          */
     96         void onTimeUpdate(TimeAnimator animation, long totalTime, long deltaTime);
     97 
     98     }
     99 }
    100